Fire Ants Riding Flood Waters

AUBURN, Ala. — Following a flood, humans and insects are generally forced from their homes in search of dry ground. In many Southern areas where Imported Red Fire Ants are common, the displacement of the insects can lead to potentially serious medical issues.

Why Do Fire Ants Float?

Floodwaters do not kill fire ants. Instead, these insects crawl out of their colonies and form a loose ball. The fire ants float until reaching dry land or an object they can crawl onto. Floating ant colonies can take several shapes: ribbons, streams or balls. The large masses of ants contain all of the members of the ant colony — worker ants, brood (eggs, larvae, pupae), winged reproductive males and females, and queen ants.

Dr. Fudd Graham, a researcher at Auburn University, said fire ants can survive for as long as two weeks as a floating raft.

“Fire ants are a native South American flood plain species,” Graham said. “These ants developed this survival skill adaptation many years ago to survive in the flood plains, so this behavior is not something new, but something the ants have been doing to survive for a long time.”

Fire Ant Control During a Flood

It is important to work carefully to avoid contact with fire ant colonies. The Alabama Cooperative Extension System’s Emergency Handbook shares these tips for avoiding a run-in with fire ants during a flood.

Avoid contact with floating mats of fire ants.

When in a rowboat, do not touch the ants with the oars.

While working in floodwater, dress appropriately. Rubber boots, rain gear, and gloves (cuffed) can help prevent ants from reaching the skin.

If ants contact skin, they will sting. They should be removed immediately by rubbing them off. The ants will cling to the skin if submerged. Even a high-pressure water spray may not dislodge them. However, a spray made of diluted, biodegradable dishwashing liquid may help immobilize and drown them.

When returning to flooded structures, floating ant masses are occasionally encountered, even indoors.

Fire Ant Control Post-flood

As floodwaters recede, fire ants will seek dry shelter on anything the floating mass comes in contact with. Debris piles and items misplaced in a flood are prime targets for fire ants until a mound can be re-established.

Colonies encountered after a flood must be dealt with carefully, and contact with a floating raft should be avoided. Graham said the time after a flood is critical, as a human may be dry ground.

“When a raft hits something solid, fire ants will immediately begin crawling up to dry ground,” he said. “If you see a floating colony, be extremely careful not to come in contact with it because you will become the dry mass they are looking for and they will crawl onto you.”

Fire ants can be under anything after the flood. Fire ants will get under furniture, carpet strips and and wood to establish a colony. Be especially careful if the area has been drying out for several days, as fire ants will have had an opportunity to begin rebuilding.

Consider spraying shoes and pants with insect repellent to keep away foraging ants off of clothing. When tools with handles, dust the handles with talcum powder. Fire ants cannot crawl on vertical surfaces dusted with the powder. Aerosol spray products containing pyrethrins or pyrethrum derivatives (tetramethrin or allenthrin), are labeled for use on ants or crawling insects, have a quick knockdown and break down quickly.